Electrophotographic developers are a dry developer in which toner components containing materials containing a colorant and a resin binder are used in a dry state, and a liquid developer in which toner components are dispersed in an insulating carrier liquid.
Liquid developers allow the toner particles to form into smaller particles, so that they give excellent image quality, thereby making it suitable for commercial printing applications. In addition, in the recent years, with the increasing demands for speeding up, liquid developers with lowered viscosities are also in demand. In other words, liquid developers in which toner particles are stably dispersed at smaller particle sizes and lower viscosities are in demand.
In addition, in the recent years, with increased awareness in environmental protection, an insulating liquid having a low volatility is being used as a disperse medium for liquid developers.
Patent Document 1 (Japanese Patent Laid-Open No. 2009-157254) discloses a liquid developer characterized in that the liquid developer contains an insulating hydrocarbon organic solvent 2-octyl-1-dodecene and/or 2-octyldodecane; colored resin particles comprising at least two components of a pigment and a resin binder undissolvable in the above solvent; a dispersant dissolvable in the above solvent; and a charge control agent, wherein a total content of the above solvent is 70% by mass or more of the entire amount 100% by mass of the insulating hydrocarbon organic solvent, for the purpose of lowering viscosity of the system and improving electrophoretic property while considering environmental issues.
Patent Document 2 (Japanese Patent Laid-Open No. Hei-6-236078, corresponding to U.S. Pat. No. 5,364,726) discloses a liquid developer containing a colorant and a substantial amount of a curable liquid vehicle having a viscosity of not greater than about 500 centi-Poise, and a resistivity of not less than about 108 ohm-cm, as a liquid developer composition having an advantage of reducing the generation of a solvent steam from a liquid development apparatus and from the printouts produced by the liquid developer.
Patent Document 3 (Japanese Patent Laid-Open No. 2005-10528, corresponding to U.S. Patent Application Publication No. 2004/0259015) discloses that high-quality images, such as ID, blurriness, and coloration, in an electrophotographic liquid developer are achieved, and the generation of a solvent steam, an odor from an insulating liquid or the like is suppressed or reduced, thereby excellent dispersibility of the colorant, high optical density, stable high-resolution, and high-chromatic fused images are obtained, and that as a liquid toner which is capable of suppressing the generation of a solvent steam during fusing and thus suitable for a process of fusing concurrently with transferring, a recording material in which a colorant is dispersed in a non-aqueous dispersion medium, characterized in that the non-aqueous dispersion medium contains at least a poly-alpha olefin.